In the production of two-tone or two-color boots from thermoplastic material, devices are used which include injection mold forms which each has two base stamps, a last and two shaped lateral form pieces. The lateral form pieces, when in their closed position with the last centered therebetween, provide a cavity in which a boot shaft is molded. A base stamp for forming the shaft base when in its closed position is adjacent to the cavity to the shaft base supporting the subsequently form the boot shaft for the outer sole.
After a textile sock (a feed-stock made of woven material) is fitted on the last, the lateral form pices are pivoted towards the last and the base stamp for forming the shaft base is pivoted and fit against the two lateral form pieces. By means of a deadhead borehole in the base stamp, material is injected into the cavity for the purpose of forming the shaft and the shaft base.
After the shaft material solidifies, the base stamp for forming the shaft base is pivoted away from the lateral form pieces and a base stamp for forming the outer sole is then pivoted against the two lateral form pieces. Thereafter, material for forming the outer sole is injected through a deadhead borehole in this base stamp into the space defined by the lateral form pieces in their closed position, by the base stamp for forming the outer sole, and by the already-molded shaft base on the last.
Generally, the production of boots from thermoplastic material can be accomplished in this fashion, particularly when the outer sole consists of a material of some color other than that of the shaft.
Difficulties arise, however, when the upper shaft flange is to be of a material of some color other than that for the shaft. In principle, it could be done such that after the molding of the shaft and molding-on of the sole, the shaft on the last with the molded sole is brought into another work station in which, with appropriate tool parts, the upper shaft flange is molded from material of the corresponding color. Experience has shown that a clear dividing line between the differently-colored upper shaft flange and the shaft cannot generally be produced. In addition, this finishing process is very time-consuming.